1. Field of the Invention
The present invention relates to a surfactant. More specifically, the present invention relates to a novel surfactant which is less irritating to the skin or the mucous membrane than prior art surfactants, which exhibits excellent hair conditioning effects and fabric softening effects, and which can be widely used in a toiletry or detergent composition or the like.
2. Related Art
A surfactant that is less irritating to the skin or the mucous membrane than prior art surfactants is preferably used in a composition of toiletries such as a face wash, a shampoo, a rinse, a hair conditioner, a body shampoo or the like and in a detergent composition. Further, hair toiletries such as a rinse, a hair conditioner, a hair treatment and the like are expected to have such conditioning effects that these toiletries make the hair smooth and suppress a dry and hard feeling.
Known examples of surfactants that are less irritating to the skin or the mucous membrane include acylamino-acid derivatives such as N-acylglutamic acid salt, N-acylglycine salt, N-acylarginine ethyl ester salt and the like. But the above-mentioned acylamino-acid derivatives give the hair low levels of conditioning effects, and these derivatives are, therefore, not satisfactory as conditioning agents such as a rinse, a hair conditioner and the like. Besides, with regard to the bubbling property, a further improvement thereof has been in demand.
As another surfactant of an amino-acid derivative type, a surfactant formed by adding a glycidyl ether to a neutral amino acid or an acidic amino acid is known. For example, N-(3-alkyl-2-hydroxypropyl)sarcosine and N,N-bis(3-alkyl-2-hydroxypropyl)glycine formed upon using sarcosine and glycine are described in E. Ulsperger, Fette, seifen, anstrichm., 68 (11), 964-967 (1966). Further, N-(3-alkyl-2-hydroxypropyl)serine, N-(3-alkyl-2-hydroxypropyl)aspartic acid and the like are described in WO 94/21595. However, these neutral and acidic amino-acid derivatives give the hair still unsatisfactory conditioning effects.
Furthermore, amino-acid derivatives formed by adding an 1,2-epoxyalkane to an amino acid are described in Japanese Laid-Open Patent Application (Kokai) No. 22,417/1973. However, these amino-acid derivatives are not said to be satisfactory in terms of solubility.
Meanwhile, an alkyl quaternary ammonium salt and the like have been widely used as conditioning agents or fabric softening agents. It has been known that these conditioning agents are electrically adsorbed on the hair surface, which is weakly acidic, or the fabric surface, which is negatively charged in the rinsing water, to impart a good combing property, a smoothness and the like to the hair. Nevertheless, they strongly irritate the skin, the mucous membrane and the like, and are problematic also in terms of biodegradability. Furthermore, they lower the hygroscopic property of fabric.